// handles positive w only
idVec4 compute_homogeneous_plane( idVec4 a, idVec4 b, idVec4 c ) {
idVec4 v, t;
if( a[3] == 0 ) {
t = a;
a = b;
b = c;
c = t;
}
if( a[3] == 0 ) {
t = a;
a = b;
b = c;
c = t;
}
// can't handle 3 infinite points
if( a[3] == 0 ) {
return v;
}
idVec3 vb = homogeneous_difference( a, b );
idVec3 vc = homogeneous_difference( a, c );
idVec3 n = vb.Cross( vc );
n.Normalize();
v.x = n.x;
v.y = n.y;
v.z = n.z;
v.w = - ( n * idVec3( a.x, a.y, a.z ) ) / a.w ;
return v;
}
polyhedron make_sv(const polyhedron &oc, idVec4 light)
{
static polyhedron lut[64];
int index = 0;
for (unsigned int i = 0; i < 6; i++) {
if ((oc.p[i].plane * light) > 0)
index |= 1<<i;
}
if (lut[index].e.size() == 0) {
polyhedron &ph = lut[index];
ph = oc;
int V = ph.v.size();
for (int j = 0; j < V; j++) {
idVec3 proj = homogeneous_difference(light, ph.v[j]);
ph.v.push_back(idVec4(proj.x, proj.y, proj.z, 0));
}
ph.p.empty();
for (unsigned int i=0; i < oc.p.size(); i++) {
if ((oc.p[i].plane * light) > 0) {
ph.p.push_back(oc.p[i]);
}
}
if (ph.p.size() == 0)
return ph = polyhedron();
ph.compute_neighbors();
MyArrayPoly vpg;
int I = ph.p.size();
for (int i=0; i < I; i++) {
MyArrayInt &vi = ph.p[i].vi;
MyArrayInt &ni = ph.p[i].ni;
int S = vi.size();
for (int j = 0; j < S; j++) {
if (ni[j] == -1) {
poly pg;
int a = vi[(j+1)%S];
int b = vi[j];
pg.vi = four_ints(a, b, b+V, a+V);
pg.ni = four_ints(-1, -1, -1, -1);
vpg.push_back(pg);
}
}
}
for (unsigned int i = 0; i < vpg.size(); i++)
ph.p.push_back(vpg[i]);
ph.compute_neighbors();
ph.v.empty(); // no need to copy this data since it'll be replaced
}
polyhedron ph2 = lut[index];
// initalize vertices
ph2.v = oc.v;
int V = ph2.v.size();
for (int j = 0; j < V; j++) {
idVec3 proj = homogeneous_difference(light, ph2.v[j]);
ph2.v.push_back(idVec4(proj.x, proj.y, proj.z, 0));
}
// need to compute planes for the shadow volume (sv)
ph2.recompute_planes();
return ph2;
}
